Many types of batteries and other power cells are known, based upon a relatively wide range of electrical couples, and among the most popular electrical couples are those containing zinc or lead.
For example, zinc is coupled with carbon in many simple flashlight batteries to provide a relatively inexpensive and reliable power source. Although manufacture of Zn/C batteries is generally simple and poses only relatively little environmental impact, various disadvantages of Zn/C batteries exist. Among other things, the ratio of power to weight in commonly used Zn/C batteries is relatively poor. Similarly, while lead is relatively inexpensive and is implemented in numerous batteries (e.g. car batteries), lead has appreciable toxicity. Furthermore, sulfuric acid spills from a typical lead-acid battery may pose a significant environmental and health hazard.
To circumvent at least some of the problems associated with acid electrolyte spills, gelling agents can be added to a lead acid battery to produce a gelled electrolyte. Gelled lead-acid battery electrolytes are generally known to reduce inadvertent electrolyte spills. Moreover, many gelled lead-acid battery electrolytes allow operation of batteries incorporating such electrolytes in tilted or even in inverted position (e.g., marine batteries). However, gelling the lead-acid battery electrolyte generally fails to reduce problems with lead toxicity and high ratio of power to weight.
To improve the ratio of power to weight, alternative zinc coupling partners and redox systems can be employed. For example, zinc can be coupled with mercury oxide or silver to achieve an improved power to weight ratio. However, the toxicity of mercury oxide is frequently problematic in manufacture and tends to become even more problematic when such batteries are discarded. On the other hand, while silver as a coupling partner for zinc is environmentally substantially neutral and significantly improves the power to weight ratio, the use of silver is in many instances economically prohibitive.
Alternatively, halogens may be employed as a coupling partner for zinc, and most common zinc-halogen couples include zinc-bromine and zinc-chloride. Zinc-halogen redox systems frequently have a relatively favorable weight-to-power ratio. Moreover, the capacity of such systems is typically only limited by the volume of the electrolyte. Consequently, zinc halogen based batteries are often employed for load leveling in power substations. However, such battery configurations are often difficult to integrate into portable or miniaturized devices Moreover, such battery configurations are often prone to leakage leading to significant problems due to the highly corrosive nature of halogens. Leakage may potentially be overcome by gelling electrolyte, however, most likely at the cost of significant disadvantages.
Among other things, pumping of gelled electrolytes from anolyte and/or catholyte reservoirs is technically challenging, if not impossible, under normal operating conditions known for such systems. Furthermore, gelling agents in such systems need not only to be electrochemically inert but also chemically inert to the corrosive nature of the electrolytes.
Alternatively, zinc air battery systems may be employed in applications where a favorable ratio of weight to capacity is particularly important. In such zinc air batteries, atmospheric oxygen is used as a gaseous coupling partner for zinc, which is typically provided in form of gelled zinc powder anodes. Among the various advantages in such batteries, using air (i.e., oxygen) as coupling partner for zinc significantly reduces weight. However, reasonable shelf life of such batteries can often only be achieved by using an airtight seal. Furthermore, to provide continuous operation, air must have an unobstructed path through the battery to the cathode so that the oxygen in the air is available to discharge the cathode. Moreover, commercial applications of zinc-air batteries have previously been limited to primary or non-rechargeable types. Experimental rechargeable zinc-air batteries have been built for use in automotive applications and typically use a liquid electrolyte that is recirculated via a pump. However, such systems are often impractical for miniature consumer applications ranging from radios to portable computers because of their mechanical complexity and lack of leak resistance.
Thus, although numerous batteries with relatively favorable weight-to-capacity ratios are known in the art, all or almost all of them suffer from one or more disadvantage. Therefore, there is still a need to provide improved batteries.